<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
<div id="app">
    <h3>v-once:是不会改变的</h3>
    <p v-once>原始值：{{msg}}</p>
    <p>后面的：{{msg}}</p>
    <input type="text" v-model="msg">
</div>
<script src=" https://cdn.staticfile.org/vue/2.2.2/vue.min.js"></script>
<script>
    let vm = new Vue({
        el: '#app',
        data: {
            msg: '你好，世界！'
        }
    });
</script>
</body>
</html>